How does a TBM work?

Click on the image and watch the video below to learn.

Swipe Sideways


This is the part that rotates and excavates the soil.

Air Lock

Acclimatises workers prior to entering and exiting the pressurised excavation chamber.

TBM Hydraulic Thrust Jacks

These jacks push the whole TBM forward by creating pressure against the installed precast concrete lining segments. This is what makes it all move forward.

Tail Skin

Protective steel skin within which the segmented precast tunnel lining is built. This area is sealed to prevent groundwater entering behind the lining.

TBM Conveyor

This is a conveyor belt system that transports excavated material away from the screw conveyor discharge to the tunnel conveyor.

Electrical Control Container

Houses the panels for the distribution and control of electrical power to the TBM’s many components.

Electrical Transformer

Changes the voltage of the incoming electrical power to a lower usable power for the motors. The electrical power runs from the transformer to the electrical control centre.

TBM Control Cabin

This is where the entire TBM and associated systems are operated (the TBM’s cockpit).

Tunnel Conveyor Transfer

This is where the tunnel spoil changes from the TBM conveyor to the tunnel conveyor belt.

Ventilation Ducts

This provides a constant flow of clean air and maintains a safe temperature for the workers.

Refuge Container

This is a safety refuge for underground personnel.

Ventilation Canister

Stores 200m of ducts which feed out as the TBM advances – similar to a telescope unfolding.

Tunnel Conveyor Belt

Material is transferred onto a conveyor belt that runs along the length of the tunnel up to the surface. Excavated material is then stockpiled on the surface and transported by trucks to designated fill sites.


Multi Service Vehicle (MSV)

Carries precast lining segments from the surface to the TBM. Also used to transport personnel in the tunnel.

Segment Crane

Lifts precast lining segments from the MSV then rotates and carries them to the segment feeder.

Bentonite Tank

Storage for ground conditioning fluids.

Bentonite Pumps

Waste Water Tank


Provides compressed air for air tools.

Cooling Unit

Hose Reels

Grease Pumps

Used for sealants and lubrication.


Powers TBM hydraulic systems.

Segment Feeder

This is a transfer system for precast tunnel lining segments.

Tunnel Lining

Concrete segments that form the tunnel.

Segment Lining Erector

This machine works just like a big robot arm. It picks up the concrete lining segments using a vacuum plate and then rotates and places them into position to form a ring.

Main Drive Unit

This unit houses the main bearing (powered by several motors) and turns the cutterhead.

Screw Conveyor

Lifts excavated material from the excavation chamber up to the TBM conveyor. It also enables operation of an earth pressure balance system used for excavating soft material. It essentially maintains the ground support and controls the excavated material transfer.


Fire System Foam